Spark plug



1.. e. WALTER ET AL March 19, 1940.

SPARK PLUG Filed Dec. 16, 1939 INVENTORS- Wm ATTORNEYS Patented Mar. 19,1940 UNITED STATES PATENT OFFICE SPARK PLUG Louis G. Walter,Philadelphia, and Harry R. Webber, Norwood, Pa.

Application December 16, 1939, Serial No. 309,528 5 Claims. (01.123-169)The object of our invention is to devise a novel spark plug, wherein theinsulation, such as for example the porcelain which carries the mainelectrode, is surrounded intermediate its ends by a chamber ventedthrough the porcelain to the atmosphere to provide for the free escapeof heat, so that, under operating conditions of an internal combustionengine, the porcelain will be maintained at a substantially uniformtemperature.

A further object of the invention a novel construction and arrangementof' a shell,

-insulation, electrodes and means for retaining the parts in assembledcondition.

With the above in view, our invention comprehends a novel constructionand arrangement of a spark plug.

It further comprehends a novel ventilated spark plug wherein a novelconstruction of an insulator is secured within a novel construction ofshell to provide a chamber surrounding the porcelain and vented throughthe porcelain to the atmosphere.

Other novel features of'construction and advantage will hereinafter moreclearly appear in the detailed description and the appended claims.

For the purpose of illustrating our invention, we have shown in theaccompanying drawing a preferred embodiment of it, which, in practice,will give satisfactory and reliable results. It is, however,.to beunderstood that this embodiment is typical only and the variousinstrumentalities of which our invention consists can be variouslyarranged and organized, and the invention is not limited to the exactarrangement and organization of these instrumentalities as herein setforth.

Figure l is a sectional elevation of a spark plug embodying ourinvention.

Figure 2 is a section on Figure 3 is a sectionon line 3-3 of Figure 1.

Similar numerals indicate corresponding parts.

Referring to the drawing:

l designates the shell of a spark plug embodying our invention. Theshell I is externally threaded as at 2 to provide for its assembly inthe cylinder head of an internal combustion engine. The shell l is alsointernally threaded at its rear end as at 3 to receive a gland 4 whichsecures an insulation member 5, commonly called the porcelain, in sealedrelation with the forward end of the shell.

The shell I is provided with a front portion 6. of reduced diameter, anintermediate portion 1, of greater diameterthan that of the frontportion 6, and a rear portion 8 of greater diameter is to devise line 22of Figure l.

' the porcelain towards than that of the intermediate portion 1., Theforward end of the chamber of the shell has a I conical or tapered seat9 provided with a gasket l0 against which the conical ortapered face llof the porcelain seats. The front end l2, of the porcelain is of lessdiameter than that of the front opening l3 in the' shell, and such frontend extends into said opening [3, and preferably through and beyond suchopening.

In rear of the seat 9 the porcelain is of less 10 diameter than thechamber M in the front portion of the shell and merges into a portioniii of reduced diameter contributing with the shell to form an enlargedchamber It. In rear of the reduced portion ii of the porcelain, ofenlarged diameter as at H, but of less diameter than the chamber of therear portion 8 of the shell. The enlarged portion ll of the porcelainmerges into a rear portion l8 of reduced diameter thereby forming ashoulder I9 to receive a gasket 20 20 against which the gland 4 bears.It will'thus be clear-that the porcelain has suflicient clearance withinthe chamber of the shell to adjust itself to the seat 9 against which itis held by a direct forward prr sure imparted by the gland 4. 25

The enlarged portion ll of the porcelain has one or more apertures 2|extending longitudinally through it and communicating with the chamber I6 and with one or more longitudinally extending grooves 22, formed inthe outer face of the por- 30 tion I B of the porcelain and'terminating'in rear of the gland 4.

It will thus be clear that the chamber I6 is at all times vented to theatmosphere.

The porcelain 5 carries a main electrode 23 3 which extendslongitudinally through it and which terminates at its forward end in apair of rearwardly curved terminals 24 which cooperate with the groundelectrodes 25.

Insteadof having the shell form the ground 0 electrodes we preferablyuse a more durable metal having a high heat resistance such as nichrome,which is in the form of pins permanently fixed in apertures in theforward end of the shell by swaging, welding or in any other suitablemanner. 45

The electrode 23 has a sealing member 26 in a recess 21 opening throughthe rear end of the porcelain.

It will be apparent from the foregoing that a pressure in a forwarddirection is exerted to press 5 its seat, to effectively seal the innerend of the ventilated chamber l6. Due to shrinkage and contraction inthe making of mensions, and by providing a clearance in the .1

the latter is 15 shell for the porcelain and a seat at the forward endportion of the porcelain a positive seal can be obtained.

The heat radiated from the shell to the chamber I 6 is vented to theatmosphere through apertures 2| and grooves 22, so that a substantiallyeven temperature is maintained between the shell and porcelain whichcontributes to proper ignition in high compression motors.

The insulator can be considered as having a claim as new and desire tosecure by Letters Patent is:

1. In a spark plug, a shell having an internal seat near its forwardend, an insulator engaging said seat andpf reduced diameter intermediateits ends to form a ventilating chamber between the insulator and'theshell, said insulator having ventilating ports communicating with saidchamber and with the atmosphere to vent said chamber to the atmosphere,a 'main electrode extending through said insulator, an electrode on theshell, and means engaging said shell to force said insulator towards itsseat.

2. In a spark plug, a shell having a tapered seat near its forward end,an insulator having a tapered portion nearits forward end and of reduceddiameters intermediate its ends to form a ventilating chamber betweenthe insulator and the shell, said insulator having ventilating portsextending longitudinally through it and communicating with said chamberto vent said chamber to the atmosphere, a main electrode extendingthrough said insulator and having its forward end provided withrearwardly deflected terminals, ground electrodes carried by said shelland a gland in threaded engagement with the shell to retain saidinsulator in sealed condition within said shell.

3. In a spark plug, a shell having a tapered seat near its forward end,an insulator of reduced diameter intermediate its ends to form with theshell a ventilating chamber having vents leading from said chamber tothe atmosphere and having a tapered seat near its forward end, agasketbetween said seats, said insulator having a shoulder intermediate itsend, a gasket between said gland and said shoulder and a gland engagingsaid last named gasket whereby pressure in only one direction is exertedagainst said insulator to seal it within said shell, a main electrode inthe insulator, and a ground electrode on the shell.

4. ma spark plug, a shell having a seat at its forward end, an insulatorhaving a seating portion cooperating with said seat and substantiallyfilling the forward end of said shell, said insulator having anintermediate portion of reduced diameter to form with the shell aventi-,

lated chamber, and having an enlarged portion in rear of said chamberwith vent ports leading to the atmosphere, a gland in threadedengagement with the shell to move said insulator toward said seat, amain electrode extending through said insulator and having its forwardend forming terminals and ground electrodes of heat resistant metalfixed in the forward end of the shell.

5. In a spark plug, a shell having a seat at its forward end, aninsulator having an enlarged head near its forward end to cooperate withsaid seat and a collar of greater diameter than that of said head inrear of and spaced from said head to ,form a ventilated chamber, agasket for said seat, a gasket for said collar, a gland engaging theshell and collar gasket to move the insulator towards said seat, saidcollar having a vent aperture leading from said ventilated chamber andmerging into a groove extending along the insulator and opening to theatmosphere in rear of said gland.

LOUIS G. WALTER. HARRY R. WEBBER.

